1. Field of the Invention
The present invention relates to a hydraulic power steering apparatus equipped with a motor-driven pump.
2. Discussion of Related Art
Japanese Patent Publication (kokoku) No. 3-29628 discloses a hydraulic power steering apparatus equipped with a motor-driven pump. In that power steering apparatus, the current of the motor for driving the pump is detected to indirectly determine the steering load, and the motor is controlled based on the detected current.
In such a power steering apparatus, the pump is driven at a low speed or is stopped when a steering wheel is not operated. Therefore, the energy required to drive the pump can be reduced.
However, in the above-described structure, the current of the motor for driving the pump is fed back to a controller so as to control the rotational speed of the motor, thereby controlling the amount of working fluid discharged from the pump. Consequently, the controller for controlling the motor becomes complicated, resulting in increased costs.